Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Contract assets	$ 1,012,109		$ 859,675
Advance billings deducted from contract assets	234,000		308,000
Information about contract liabilities:
Revenue recognized that was included in contract liabilities as of January 1	836,000	$ 674,000
Unbilled Receivables
Disaggregation of Revenue [Line Items]
Contract assets	724,000		590,000
Contract Work in Progress
Disaggregation of Revenue [Line Items]
Contract assets	$ 288,000		$ 270,000